| 摘要 |
The proposed gravel pack evaluation tool includes a 14 MeV neutron source and one (or two) gamma rays detector; the emitted neutrons activate the Al and Si atoms of the pack, ie they cause Al/Si atoms to transmute in an unstable state which in turn decays back to a stable state while emitting gamma rays. Advantages are: (i) no chemical nuclear source; (ii) allows evaluation of gravel pack having density close to completion fluid density; (iii) shallow depth of investigation; (iv) reduced influence of atoms non representative of the gravel pack (e.g. 016) by choosing a logging speed related to the half life of the gamma rays characteristic of 016 atoms. Furthermore, the combination of this tool with a known TDT allows to determine any zone where the original pack has been pulled away in the tubing with the producing oil and replaced by formation material, such emptied-and-formation-refilled pack being representative of a damaged screen area. |
